MYELIN PROTEINS FROM DIFFERENT REGIONS OF THE CENTRAL NERVOUS SYSTEM

—The protein composition of myelin prepared from specific anatomical regions of the bovine brain and spinal cord was studied by a modification of the method of Gonzalez -Sastre (1970). Spinal cord myelin contained lesser amounts of chloroform-methanol soluble protein and proteolipid protein and had a lower activity of the enzyme 2′,3′-cyclic nucleotide 3′-phosphohydrolase than did myelin from subcortical white matter. There was no difference, however, in the protein composition of myelin from the various levels of the spinal cord. The amino acid composition of both proteolipid and basic protein showed no significant regional differences. Myelin preparations from both brain and spinal cord contained DM-20 protein.     

ULTRAVIOLET ABSORPTION CHARACTERISTICS OF MYELIN FROM THE CENTRAL NERVOUS SYSTEM

—New data are presented and published data reviewed to show that the protein content of rat brain myelin must be close to 21 per cent. Ultraviolet absorption measurements in the 220 nm region, however, indicate an apparent protein content of 44·3 per cent which, after solubilization with lysophosphatidylcholine falls to 35·8 per cent. It is shown that this latter proportion can be accounted for in terms of u.v. absorption by myelin protein and lipids, contributions being made by sphingolipids, phospholipids and cholesterol. It is concluded that in the environment of the intact myelin structure, u.v. absorption due to some of the chromophores is enhanced and that this effect is relaxed by lysophosphatidylcholine solubilization. Supportive evidence is given from measurements in the 280 nm region.     

PURIFICATION AND PROPERTIES OF CHOLINE ACETYLTRANSFERASE FROM THE NERVOUS SYSTEM OF DIFFERENT INVERTEBRATES

—Choline acetyltransferase has been purified from three invertebrate species, namely snail (Helix aspersa), cockroach (Periplaneta americana) and horse shoe crab (Limulus polyphemus.) All three enzymes followed a Theorell-Chance enzyme mechanism with a sequential addition of the substrates. All three enzymes were activated by sodium and potassium chloride and inhibited by high concentrations of magnesium or calcium chloride. The apparent K_m for choline and acetyl-CoA was for snail: K_mch= 370 μm ,K_mAcetyl-CoA= 51μm ; cockroach:K_mCh= 550 μm , K_mAcely-CoA= 16 μm horse shoe crab:K_mCn= 2700 μm K_mAcctyl-coA= 68 μm CoA inhibited the enzymes competitively with respect to acetyl-CoA and non-competitively with respect to choline. Acetylcholine inhibited the enzymes competitively with respect to choline and non-competitively with respect to acetyl-CoA. All the enzymes were inhibited strongly by 5,5′-dithiobis (2-nitrobenzoate), iodoacetate, acryloylcholine, chloracetylcholine and 3-bromacetonyltrimethyl-ammonium. The enzymes were only weakly inhibited by the styrylpyridine derivatives. The isoelectric points were 5.3 and 5.0 for the horse shoe crab and cockroach enzymes respectively. All three enzymes showed low affinity for a cation-exchanger (CM-Sephadex).     

INITIATION AND MODIFICATION OF RHYTHMIC BUCCAL MOTOR OUTPUT IN THE ISOLATED CENTRAL NERVOUS SYSTEM OF LYMNAEA STAGNALIS

The neural circuitry underlying generation of rhythmic feedingmovements in Lymnaea stagnalis has been described in detail.Three types of higher order inter-neurone modulate the outputof the feeding rhythm generator. When stimulated, the Slow Oscillatorand Cerebral Ventral 1 interneurones initiate and maintain patternedmotor output. The serotonergic Cerebral Giant Cells (CGCs) canalso initiate the rhythm, but may suppress or abolish an ongoingrhythm. Application of serotonin to the central nervous systemmimicks the effects of stimulating the CGCs. Another monoamine,dopamine, reliably activates the feeding rhythm generator. Otherneuroactive substances, acetylcholine and FMRFamide, inhibitrhythmic motor output. The variety of routes by which feeding motor output may be controlledexperimentally suggests that the system is highly flexible.This would allow for adaptation to a range of sensory environments.     

HEXAGONAL ARRAY OF SUBUNITS IN TIGHT JUNCTIONS SEPARATED FROM ISOLATED RAT LIVER PLASMA MEMBRANES

Solubilization of isolated rat liver plasma membranes in 1% deoxycholate and centrifugation yielded a fraction (pellet) that consisted mainly of tight junctions (zonulae occludentes). An hexagonal array of subunits similar to that previously found in a number of the unfractionated plasma membranes was demonstrated in all the membrane sheets of these preparations by negative staining. It is concluded that the hexagonal subunit pattern is present in the tight junctions, and that this structural differentiation may be related to the intercellular diffusion afforded by the junctional membrane.     

COMPARATIVE PEPTIDE MAPPING AND ISOELECTRIC FOCUSING OF ISOLATED SUBUNITS FROM CHICK EMBRYO BRAIN TUBULIN

The α- and β-subunits of chick embryo brain tubulin have been isolated under denaturing conditions and compared with respect to their molecular weight, amino acid composition, tryptic peptide maps, amide content and isoelectric focusing properties. An 8 M-Urea-containing polyacrylamide gel system with varying acrylamide concentrations was used for calculation of the retardation coefficients (K_R) of the tubulin subunits. A molecular weight of 53,000 was estimated for each subunit by comparison to K_R values for standard proteins. Amide contents of approx 41% of the carboxyl groups of α-tubulin and 48% of the carboxyl groups of β-tubulin were calculated using the average PI value, the pK_intrinsic for the ionizable side chains of the amino acids and the amino acid composition of each subunit. Comparative peptide maps of trypsin digested α- and β-tubulin demonstrated 16 peptides unique to each subunit and 23 peptides which comigrate. Both subunits give rise to multiple species on electrofocusing gels. The average isoelectric points for the α- and β-subunits are 5.4 and 5.2, respectively.     

ISOLATION OF AXONAL VARICOSITIES (AUTONOMIC SYNAPTOSOMES) FROM THE ENTERIC NERVOUS SYSTEM

Abstract— A subcellular fraction enriched with varicosities of autonomic axons was obtained from homogenates of strips of guinea-pig longitudinal muscle and adherent myenteric plexus using differential and sucrose-or Ficoll-density gradient ultracentrifugation. This fraction contained the marker, [G-³H]5-hydroxytryptamine (5-HT), taken up by serotonergic axon terminals present in the preparation during a period of incubation prior to homogenization. Electron microscopic examination showed that the isolated varicosities resembled CNS synaptosomes in containing vesicles and mitochondria but, as is characteristic of autonomic postganglionic terminals, they lacked synaptic membrane specializations. Quantitative electron microscopic radioautography revealed that [G-³H]5-HT was confined to isolated varicosities. Isolated varicosities were capable of taking up and sequestering 5-HT from the surrounding medium; this uptake was temperature-sensitive and blocked by fluoxetine. The subcellular distribution of [G-³H] l -tryptophan was also studied by subfractionation of strips in an attempt to determine which structures were responsible for the high-affinity uptake of that amino acid. Although most of the [G-³H] l -tryptophan was found in the high-speed supernatant, particulate [G-³H] l -tryptophan was most concentrated in the subcellular fraction containing isolated axonal varicosities. These studies indicate that a fraction containing functional serotonergic varicosities can be isolated from the gut. These varicosities are probably one of the elements responsible for the high-affinity uptake of l -tryptophan by the myenteric layer of the gut.     

中国水蛇的神经系统

本文报道中国水蛇神经系统的大体解剖,其中,对三叉神经叙述较详。     

FINE STRUCTURE OF THE NERVOUS SYSTEM OF HYDRA

Fine structural details of the cells and processes of the hydranenous system are reported in this paper. Ganglion cells aresmall bipolar or multipolar cells situated above the muscularprocesses of epitheliomusiular cells. An elaborate Colgi apparatusconsisting of parallel lamellae and small and large vesiclesis present in these cells. Some cells are poor in ribosomeswhile others contain numerous free ribosomes. In the ribosome-richcells, small membranous microtubules originating from the nuclearenvelope extend into the cytoplasm and neurites. The neuritesalso contain vesicles and mitochondria and terminate at thebases of cnidoblasts and on the muscular processes of epitheliomuscularcells. Specialized synapses were not observed. A second cell type contains many membrane-bounded dense granules,1000 A in diameter, and these are considered to be neurosecretorycells. Neurosecretory granules on cnidoblasts and epitheliomuscularcells. Sensory cells are small elongated cells originate inthe Golgi apparatus and are abundant in neurites which alsoterminate situated between the apical surfaces of epithelialand digestive cells. These cells are characterized by an apicalspecialization which appears to be a modified cilium. Neurosensorycells were also observed. The intimate connection of the nervoussystem with cnidoblasts suggests a role in nematocyst discharge.The finding of neurosecretory material supports the hypothesisthat the neural control of regeneration in hydra is regulatedby material released at nerve endings.     

THE CENTRAL NERVOUS SYSTEM OF CHAMELEON VULGARIS

An analysis of the brain of Chameleon has given evidence of a number of modifications in the general plan of the reptilian nervous system. The telencephalon shows a reduced olfactory mechanism and suggests the presence of the true motor cortex. The ventral peduncle of the lateral forebrain bundle is unusually large with the majority of its fibres terminating in two new nuclear masses in the hypothalamus, the nucleus entopeduncularis, and a few in the nucleus ruber. A high degree of effective response to optic stimuli is indicated by the extensive correlation between the optic tectum and the nuclear masses of the midbrain and the diencephalon. The wide range of eye movements is probably correlated with the development of the basal optic root ganglion and its numerous secondary connections and the elaborate relationship of the geniculate complex. The usually highly developed tecto-bulbar system is partly replaced by a large tegmento-bulbar system that relays the tectal impulses caudally. An interesting mesencephalic nucleus is a large nucleus profundus mesencephali that receives a great variety of impulses and appears to be an important correlation center. Ascending visceral mechanisms were described bringing the hypothalamus into relationship with the lower centers. The great excursion of the tongue is associated with a highly differentiated hypoglossal nucleus. Components of the medial lemniscus from the spinal cord and the medulla to the vicinity of the thalamus were demonstrated.     

脉红螺（Rapana Venosa）神经系统解剖的初步研究

本文对腹足纲、狭舌目、骨螺科的脉红螺神经系统的大体解剖和组织学进行了初步研究。脉红螺神经系统头向集中程度较高,神经节愈合现象较为明显。切片上观察,中枢神经节均由神经节被膜、胞体区和神经纤维网构成;形态上相似的神经细胞有集中分布的现象。